Image processing apparatus and method and storage medium

ABSTRACT

It is an object to provide an adding technique for enabling additional information to be certainly decoded from an image to which two or more kinds of additional information was added to an input image so that it is difficult to discriminate by the human eyes. To accomplish this object, for example, a plurality of kinds of additional information is periodically added to the input image at different periods so that it is difficult to discriminate by the human eyes. The image to which those additional information was added is outputted to an image forming unit.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to image processing apparatus and methodhaving a function to add additional information to an input image andrelates to a storage medium in which such a method has been stored.

[0003] 2. Related Background Art

[0004] In recent years, the performance of an image processing apparatussuch as color printer, color copying apparatus, or the like has beenimproved and an image of a high picture quality can be provided. Thus,an image can be being formed with a picture quality almost similar tothat of a bill, securities, or the like.

[0005] However, the formation of such an image is inhibited and it isnecessary to suppress such illegal behavior. As one of countermeasuresfor this purpose, there has been known a technique to bury a dot patternshowing the numbers (information such as manufacturing number, productnumber, user ID, and the like) which are peculiar to the imageprocessing apparatus into each image to be formed. By performing such aprocess, even if an image is illegally formed, by analyzing the dotpattern buried in the formed image, various situations at a time whenthe image is formed can be also known.

[0006] The dot pattern is periodically buried into the whole image everypredetermined periods. Therefore, even if only a part of the imageexists, since the information has been buried in this partial portion,the search of the various information as mentioned above can beexecuted.

[0007] To perfectly search the various information, an area of thepartial portion in the image needs to be set to an area corresponding toat least one period among the above periods.

[0008] A conventional adding method of the dot pattern (additionalinformation) as mentioned above differs every manufacturer whomanufactures each of the image processing apparatus. To decode theadditional information such as a manufacturing number and the like onthe basis of a certain formed image, it is necessary to sequentially usea decoding method corresponding to the adding method of eachmanufacturer.

[0009] However, hitherto, there is a problem such that the additionalinformation (manufacturing number, product number, user ID, and thelike) added to the image which is finally formed cannot be decoded atall due to a cause such that the image process of the input image hassome periodic trouble, the original image contents are periodic, or thelike.

[0010] Particularly, the problem as mentioned above is likely to occurin the case where an area of the formed image is small like a stamp orthe like rather than the case where an area of the formed image is largelike a bill or the like.

[0011] Hitherto, in the case where the number of manufacturers whomanufacture the apparatuses is large, there is a problem such that aload to sequentially use the decoding methods as mentioned above islarge. In particular, such a problem typically appears in case ofperforming the above decoding by a software process or the like.

SUMMARY OF THE INVENTION

[0012] The invention is made in consideration of the foregoingconventional technique and it is an object to provide an addingtechnique for enabling additional information to be certainly decodedfrom an image obtained by adding two or more kinds of additionalinformation has been added to an input image so that it is difficult todiscriminate by the human eyes.

[0013] For example, it is an object of the invention to enableinformation having a high significance to be decoded as much as possiblein case of burying two or more kinds of additional information into aninput image.

[0014] To accomplish the above objects, according to one preferredembodiment of the invention, there is provided an image processingapparatus comprising:

[0015] adding means for periodically adding first additional informationto an input image by a first period so that it is difficult todiscriminate by the human eyes and for periodically adding secondadditional information different from the first additional informationby a second period different from the first period so that it isdifficult to discriminate by the human eyes; and

[0016] output means for outputting the image to which predeterminedadditional information was added by the adding means to an image formingunit.

[0017] According to another embodiment, there is provided an imageprocessing apparatus comprising:

[0018] adding means for adding information consisting of firstadditional information and second additional information to an inputimage every unit area which is periodically assigned;

[0019] switching means for switching a positional relation between anarea showing the first additional information and an area showing thesecond additional information in the unit area; and

[0020] output means for outputting the image to which predeterminedadditional information was added by the adding means to an image formingunit.

[0021] According to still another embodiment, there is provided an imageprocessing apparatus comprising:

[0022] adding means for adding first additional information to an inputimage by a first method so that it is difficult to discriminate by thehuman eyes and for adding second additional information by a secondmethod so that it is difficult to discriminate by the human eyes; and

[0023] output means for outputting the image to which predeterminedadditional information was added by the adding means to an image formingunit,

[0024] wherein the first additional information is information which canspecify the second method.

[0025] According to further another embodiment, there is provided animage processing apparatus comprising:

[0026] adding means for adding first additional information including anerror correction code having a first error correcting ability to aninput image so that it is difficult to discriminate by the human eyesand for adding second additional information including an errorcorrection code having a second error correcting ability different fromthe first error correcting ability so that it is difficult todiscriminate by the human eyes; and

[0027] output means for outputting the image to which predeterminedadditional information was added by the adding means to an image formingunit.

[0028] The above and other objects and features of the present inventionwill become apparent from the following detailed description and theappended claims with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a detailed diagram of an additional dot generation unit212;

[0030]FIG. 2 is a diagram showing a state where AddOn dots were added;

[0031]FIG. 3 is a diagram showing an example of an image processingapparatus;

[0032]FIG. 4 is a diagram showing a procedure for image processes;

[0033]FIG. 5 is a detailed diagram of the basic additional dotgeneration unit 212;

[0034]FIG. 6 is a diagram showing a state in a register;

[0035]FIG. 7 is a diagram showing an example of AddOn dots;

[0036]FIG. 8 is a diagram showing a state where the AddOn dots wereadded;

[0037]FIG. 9 is a diagram for explaining an adding method of an AddOnpattern;

[0038]FIG. 10 is a diagram showing a state where the AddOn dots wereadded;

[0039]FIG. 11 is a diagram showing an example of an image processingapparatus;

[0040]FIG. 12 is a diagram showing a state where additional informationwas added to an input image;

[0041]FIG. 13 is a diagram showing a state of a register to store atracking code (additional information);

[0042]FIG. 14 is a block diagram of an AddOn dot adding processing unit;

[0043]FIG. 15 is a diagram for explaining an expressing method ofinformation by AddOn dots;

[0044]FIG. 16 is a diagram showing a code shown by each AddOn line;

[0045]FIG. 17 is a diagram showing parity bits of a manufacturer ID;

[0046]FIG. 18 is a diagram showing a procedure for decoding additionalinformation from an image to which the additional information was added;and

[0047]FIG. 19 is a conceptual diagram of additional information of amanufacturer ID, a product name, and a manufacturing number.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] The first embodiment of the present invention will now bedescribed hereinbelow.

[0049]FIG. 3 is a diagram showing an image processing apparatus using acolor electrophotographing technique which is used in the embodiment. Inthe diagram, reference numeral 214 denotes a printer controller(hereinafter, referred to as a controller), which will be explainedhereinlater. The controller receives image data of R, G, and B eachconsisting of eight bits per color inputted from a host computer servingas external equipment, executes well-known color image processes, andafter that, outputs the processed image data to a printer engine at thepost stage as image data of M (magenta), C (cyan), Y (yellow), and K(black) each consisting of 8 bits per color.

[0050] Reference numeral 215 denotes a printer engine (hereinafter,referred to as an engine), which will be explained hereinlater. Theengine outputs the inputted color image data of MCYK as a laser beam Lmodulated on the basis of an image of each color.

[0051] A charging device 101 uniformly charges a photosensitive drum 100to a predetermined polarity. For example, a first latent image is formedin magenta onto the photosensitive drum 100 by an exposure of the laserbeam L.

[0052] In this case, a predetermined development bias voltage issubsequently applied to only a developing device Dm of magenta. A latentimage of magenta is developed. A first toner image of magenta is formedon the photosensitive drum 100.

[0053] A transfer paper P is fed at a predetermined timing. Just beforethe front edge of the paper reaches a transfer start position, atransfer bias voltage (+1.8 kV) of a polarity (for example, pluspolarity) opposite to the polarity of toner is applied to a transferdrum 102. The paper is electrostatically adsorbed onto the surface ofthe photosensitive drum 100. After that, the first toner image on thephotosensitive drum 100 is transferred onto the transfer paper P and, atthe same time, the transfer paper P is electrostatically adsorbed ontothe surface of the transfer drum 102. Subsequently, the magenta tonerremaining on the photosensitive drum 100 is removed by a cleaner 103,thereby preparing for the latent image formation and a developing stepof the next color.

[0054] A second latent image of cyan is subsequently formed on thephotosensitive drum 100 by the laser beam L. The second latent image onthe photosensitive drum 100 is formed by a developing device Dc of cyan,so that a second toner image is formed. The second toner image of cyanis transferred onto the transfer paper P so as to be matched to theposition of the first latent image of magenta which has already beentransferred onto the transfer paper P. In the transfer of the tonerimage of the second color, a bias voltage of +2.1 kV is applied to thetransfer drum 102 just before the transfer paper P reaches the transferunit.

[0055] Similarly, third and fourth latent images of yellow and black aresequentially formed on the photosensitive drum 100 and are sequentiallydeveloped by developing devices Dy and Db, respectively. Third andfourth toner images of yellow and black are sequentially transferred soas to be matched to the position of the toner image which has alreadybeen transferred to the transfer paper P. Thus, the toner images of fourcolors are formed on the transfer paper P in an overlapped state.

[0056]FIG. 4 is a block diagram showing an image processing procedure.Color image data of RGB is transmitted in parallel from a host computer201 serving as external equipment and is inputted to the controller 214.

[0057] A color conversion processing unit 202, a γ (gamma) correctionunit 203, and a half tone processing unit 204 are arranged in thecontroller 214. Processes such as masking and UCR are executed to theinputted RGB signals by the color conversion processing unit 202 and acolor correction and an undercolor removal are executed, so that theyare converted into image data of magenta (M), cyan (C), yellow (Y), andblack (K). Since the image processing apparatus prints every pictureplane of each color of Y, M, C, and K, the image data is areasequentially outputted from the color conversion processing unit 202,namely, in accordance with the order of the data of one picture plane ofM, the data of one picture plane of C, the data of one picture plane ofY, and the data of one picture plane of K.

[0058] Subsequently, the image data is corrected by the γ correctionunit so that an output density curve becomes linear. A half tone processis executed by the half tone processing unit 204 by a method such assystematic dither method, error diffusing method, or the like.

[0059] After the above processes were executed in the controller 214,the image data of M, C, Y, and K is area sequentially inputted to theengine 215.

[0060] The engine 215 is constructed by an AddOn adding processing unit205, a PWM (Pulse Width Modulation) processing unit 206, a laser driveunit 207, an additional dot generation unit 212, an EEPROM 213, and thelike.

[0061] The AddOn adding processing unit 205 buries encipheredinformation (dot pattern) as necessary into the image data of M, C, Y,and K inputted from the controller 214 in accordance with the signalwhich is inputted from the additional dot generation unit 212 andoutputs the resultant image data to the PWM processing unit 206. In theembodiment, an AddOn pattern is added to only the image data of yellow(Y) which is inputted and the resultant image data is outputted. This isbecause a feature such that the image of yellow (Y) is difficult to bediscriminated by the human eyes rather than the images of the othercolors (M, C, K) is used.

[0062] After that, the image data is pulse width modulated by the PWMprocessing unit 206 and is D/A converted. After that, the convertedanalog signal is inputted to the laser drive unit 207 and is printed.

[0063] A CPU 302 is provided in the engine 215 and executes a control ofeach block in the engine and transmission and reception of data to/fromthe respective blocks.

[0064]FIG. 5 is a block diagram of the basic additional dot generationunit 212 to bury additional information into an image. Fake trackingcodes (additional information) stored in the EEPROM 213 are loaded intoa register 301 in the CPU 302 when the image processing apparatus isactivated.

[0065]FIG. 6 shows an internal construction of the register 301. Codesare stored in addresses F000 to F005 in the register. Total twelve bitsconsisting of eight bits of the address F000 and upper four bits of theaddress F001 shown in hatched portions in the diagram correspond to anarea to store a code of a manufacturer ID (ID of the manufacturer whomanufactured the image processing apparatus, printer controller 214, orprinter engine 215). Among them, 8 bits indicate the code of the actualmanufacturer ID and remaining 4 bits are parity bits for parity check.

[0066] Codes of the factory ID of the manufacturer who manufactured theimage processing apparatus, the apparatus number, the model number, andthe like are stored in the other areas (lower four bits of the addressF001 and the addresses of F002 to F005). The parity bits for paritycheck are also similarly added and stored in those registers.

[0067] When the image processing apparatus starts the printingoperation, those values are enciphered by an encipherment circuit 305and a parity is checked by a parity check 306. If there is an errorhere, the printing operation is stopped.

[0068] A main scan counter 307 transmits an ON signal at a positionwhere AddOn dots should be added in accordance with a clock signal PCLKin the main scan direction of the image data. A subscan counter 308performs a counting operation in response to a clock signal BD in thesubscan direction and transmits an ON signal in an AddOn line. An AddOndot generation circuit 309 receives an AddOn dot shape parameter whichis stored in an ROM 303 of the CPU. The circuit 309 generates AddOn dotsonly when all of an AddOn permission signal which is turned on only whenthe yellow data is transmitted, the main scan counter 307, and thesubscan counter 308 are ON. In an FF (the highest density) area, K isset to ON and in a 00 (the lowest density) area, WH (white) is set toON, and they are transmitted. In the AddOn adding processing unit 205 inFIG. 4, when K is inputted, the image data at the position of thecorresponding image is forcedly modulated to the highest density. WhenWH is inputted, it is modulated to the lowest density.

[0069]FIG. 7 is an example (enlarged diagram) of the AddOn dots. Abroken line in the diagram shows an AddOn line (in the embodiment, it isassumed that one AddOn line has a thickness of four pixels) of the n-thline in the image. Reference numeral 404 denotes an AddOn dot and 405indicates an enlarged dot of the AddOn dot. The AddOn dot is formed byan FF area 401 and 00 areas 402 and 403 located on both sides of the FFarea 401. As mentioned above, the AddOn dot 404 is added to the AddOnline for a multi-value image (plane of yellow). As will be explainedhereinlater, a phase difference between the AddOn dots can be used asvarious additional information.

[0070]FIG. 8 shows a state of a formed image in the yellow plane derivedby the addition of the basic additional information (AddOn dot) executedby the additional dot generation unit 212 in FIG. 5. Reference numeral1201 corresponds to the AddOn dots 404 and 405.

[0071] An area 1202 shown by a×b denotes a size of image area which canexpress all of the additional information, namely, an image size of oneperiod to add the additional information. All of the codes stored in theregister in FIG. 6 can be expressed by the dots added in the area 1202.

[0072] A plurality of AddOn dots 1201 in the area 1202 are repetitivelyadded to the whole image. In the present description, 16 lines 1203called AddOn lines exist in the area of one period in the main scandirection. The AddOn dots 1201 are arranged one by one on each AddOnline.

[0073] By adding reference dots 1204 onto the zeroth and seventh AddOnlines, the start (head AddOn line) of one period and the direction ofthe AddOn line can be specified. The manufacturer ID and the otheradditional information (factory ID, apparatus number, model number, andthe like) added by the additional dot generation unit 212 in FIG. 5 arealways added at predetermined positions in the area 1202, respectively.Specifically speaking, four AddOn lines from the head correspond to theportion which always shows the manufacturer ID and the remaining AddOnlines correspond to the portion showing the other additionalinformation.

[0074] How to show various codes (additional information) by a pluralityof AddOn dots will now be described with reference to the drawings. FIG.9 enlargedly shows the n-th and (n+1)th AddOn lines.

[0075] T denotes the repeating period of the AddOn pattern in the mainscan direction. That is, AddOn dots 901 and 903 have similar roles andinformation is not shown by AddOn dots 901 and 902.

[0076] In the embodiment, it is assumed that information is expressed bya phase difference between the AddOn lines before and after the presentline in the area 1202. By assigning phase differences like 0 to 7 in thediagram, information of three bits can be shown by each AddOn line.Since there are 16 AddOn lines in FIG. 8, information of 48 bits can beexpressed and all of the codes stored in the register 301 can be added.

[0077] In FIG. 9, t denotes a phase difference between the AddOn dots901 and 903 and shows 3-bit information of “2”, namely, “010” in thiscase.

[0078] The basic construction when adding additional information to theinput image has been described above. A characteristic construction ofthe embodiment will now be described hereinbelow.

[0079] In the embodiment, a construction of the foregoing additional dotgeneration unit 212, namely, a method of adding the manufacturer ID andthe other information differs. The adding method will now be describedin detail hereinbelow. Since the basic construction of the imageprocessing apparatus shown in FIGS. 3 and 4 is similar to that mentionedabove, its description is omitted.

[0080]FIG. 1 is a detailed diagram showing the additional dot generationunit 212, EEPROM 213, and CPU 302 in the embodiment. Component elementssimilar to those in FIG. 5 are designated by the same reference numeralsand their descriptions are omitted.

[0081] The fake tracking codes (additional information) stored in theEEPROM 213 are loaded into the register 301 in the CPU 302 when theimage processing apparatus is activated. Data which is loaded into theregister 301 is data similar to that in FIG. 6.

[0082] Reference numerals 501 and 502 denote switching units forsimultaneously performing the switching operations, which will beexplained hereinlater, by the CPU 302 every predetermined AddOn linewhen the Addon dots showing the manufacturer ID are formed and when theAddOn dots showing the other additional information are formed.

[0083] The CPU 302 has the switching unit 501 for counting the AddOnlines by counting the BD signal which is inputted and for switching soas to read out necessary codes every predetermined AddOn line on thebasis of pattern information stored in the ROM. In the switching, acontrol signal SEL is generated from the CPU 302 for always counting theBD signal so that the addition of dots, which will be explainedhereinlater, is executed.

[0084] Explanation will now be made hereinbelow with respect to acontrol such that all of the various additional information is notalways added at fixed periods but important information (themanufacturer ID in the embodiment) in the plurality of additionalinformation is added while changing the period.

[0085] First, when the image processing apparatus starts the printingoperation, the control signal SEL to control so as to read out 12 bits(including the parity bits) showing the manufacturer ID in the register301 is outputted from the CPU 302 to the switching unit.

[0086] Subsequently, the control signal SEL to control so as to read outthe codes showing the other additional information (manufacturer ID,apparatus number, model number, and the like) as much as onlypredetermined AddOn lines is outputted from the CPU 302 to the switchingunit.

[0087] For the above period of time, the CPU 302 always counts the AddOnlines. Therefore, for example, in case of sequentially adding the otheradditional information in accordance with the order of the manufacturerID→apparatus number→model number, when reaching a predetermined numberof AddOn lines at which the addition of the codes showing themanufacturer ID and the apparatus number is finished, the control signalSEL to control so as to read out the code showing the manufacturer ID isagain outputted from the CPU 302 to the switching unit.

[0088] When the reading of the manufacturer ID is subsequently finished,the control signal SEL to control so as to read out the model numberinstead of the manufacturer ID and the apparatus number is outputtedfrom the CPU 302 to the switching unit.

[0089] When the reading of the model number is finished, the controlsignal SEL to control so as to read out the code indicative of themanufacturer ID is again outputted from the CPU 302 to the switchingunit.

[0090] By repeating the above processing steps, while the information ofa relatively low significance is added one by one, two importantinformation such as a manufacturer ID can be added.

[0091] In order to easily execute the foregoing control of AddOn lines,it is desirable that the AddOn lines corresponding to the codes showingthe manufacturer ID, apparatus number, and model number are independent.However, even if such a construction is not used, it is possible tosufficiently execute. In this case, it is sufficient that the controlsignal SEL performs the read control on a unit basis of bits (3 bits inthe embodiment) which can express one AddOn line instead of performingthe read control every kind of additional information as mentionedabove.

[0092] The code which was read out while performing the above control isenciphered by the encipherment circuit 305 in a manner similar to theencipherment circuit 305 in FIG. 5. A parity is checked by the paritycheck 306. If an error occurs here, the printing operation is stopped.

[0093] The subsequent process to add the AddOn dots is similar to thatin FIG. 5.

[0094]FIG. 2 is a diagram showing a state when AddOn dots (additionalinformation) is added by using the additional dot generation unit 212 inFIG. 1.

[0095] A meshed area 702 shown by A×B corresponds to the area 1202 inFIG. 8, namely, to an image area of a unit period which can show all ofthe information.

[0096]FIG. 2 differs from the case of FIG. 8 with respect to a pointthat the number of AddOn lines showing the manufacturer ID is doubled (8lines). Therefore, the number of necessary AddOn lines is equal to 20.

[0097] Each dot 701 is the same as the AddOn dot in FIG. 8 and is shownin FIG. 7.

[0098] In the diagram, an area (for example, AddOn lines 1 to 4) shownby A×C and an area (for instance, AddOn lines 11 to 14) shown by A×Dcorrespond to the AddOn lines indicative of the manufacturer ID.

[0099] In the embodiment, among a plurality of additional informationwhich is added to the image, since the manufacturer ID is set to theinformation which needs the maximum decodability, it is controlled sothat the manufacturer ID is added twice in a unit area (area 702).

[0100] Thus, even if there are causes of periodic elements such as inthe case where a dot image similar to the dot 701 periodically exists inan image to which additional information should be added (in the casewhere the original image is an image such that a dot image always existsin the area of A×C at the same period as that in the area 702), in thecase where there is always a trouble or the like of the image process inthe area of A×C at the same period as that of the area 702, or the like,since the same information exists in the area of A×D in the area 702,the additional information (manufacturer ID in this case) can becertainly decoded.

[0101] Although the important information has been set to themanufacturer ID in the above embodiment, the invention is not limited toit. The user ID or the factory ID can be also used as importantinformation.

[0102] In the above embodiment, each time the other information is addedonce, the important information is added twice. However, the inventionis not limited to such a method but the important information can bealso added a plurality of number of times such as three or more times inaccordance with the importance.

[0103] Each time the other information is added once, the importantinformation is not added a plurality of number of times but the positionof the AddOn line showing the important information can be also variedin the area of the unit period (702 in FIG. 2, 1202 in FIG. 8).

[0104]FIG. 10 is a diagram showing a state where the additionalinformation was added by using the above method. An outline of thediagram is similar to FIG. 8. FIG. 10 differs from FIG. 8 with respectto a point that four AddOn lines to show the important information(manufacturer ID in this case) change on the area 1202. In the diagram,in an area 1202 a at the first left upper position of the image, an areaE₁ of the first four AddOn lines is an area showing the importantinformation. On an area 1202 b, an area E₂ of the last four AddOn lineschanges to the area to indicate the important information. Subsequently,the position of the four AddOn lines to show the important informationis changed like E₃, E₄, . . .

[0105] Thus, even if there is a cause of periodic elements such as inthe case where a dot image similar to the dot 1201 periodically existsin an image to which the additional information should be added, in thecase where a trouble or the like in the image process always exists inthe area of E₁ at the same period as that in the area 702, or the like,the additional information can be certainly decoded.

[0106] In the above embodiment, as for the AddOn dots, the additionalinformation is added by the dots 404 and 405 constructed by combiningthe FF area and 00 area as shown in FIG. 7. However, the invention isnot limited to such a method. Dots can be also formed by performing amodulation of +α to the original image with respect to the areacorresponding to the FF area and by executing a modulation of −α to thearea corresponding to the 00 area.

[0107] According to this-construction, since the density of the originalimage is substantially preserved, the deterioration in picture qualitycan be suppressed as much as possible.

[0108] According to the invention as described above, in the case suchthat the additional information is added to the input image a pluralityof number of times, a situation such that the additional information tobe added becomes difficult to be decoded due to causes of some periodicelements such that at least a part of the input image is periodical, atrouble or the like in the image process is periodical, or the like canbe avoided. Particularly, in case of burying a plurality of kinds ofadditional information to the input image, the information having highsignificance can be decoded as much as possible.

[0109] As a second embodiment of the invention, an image processingapparatus using a color electrophotographing technique is shown.However, the invention is not limited to it but can be also applied toan image processing apparatus using a technique such as ink jet system,thermal transfer system, or the like. The invention is not limited tothe apparatus invention but a method of performing the processes, whichwill be explained hereinlater, software to perform this method, and thelike are also incorporated in the present invention.

[0110] In the embodiment, it is now assumed that the image data which isinputted is multi-value image data of M (magenta), C (cyan), Y (yellow),and K (black) each consisting of 8 bits per color and the multi-valueimage data is area sequentially inputted.

[0111] It is also assumed that the image processing apparatus (laserbeam printer) of the embodiment has a resolution of 600 dpi and the dotpattern showing the additional information for fake tracking is added toonly the plane of Y. By using this method, it is possible to constructsuch that the additional information is difficult to be discriminated bythe human eyes as much as possible. Even a color image to which theadditional information was added can be used in a manner similar to theoriginal color image before the additional information is added. Theinvention is not limited to the case of adding the additionalinformation for fake tracking. In other words, a case where the name ofauthor who made the original image or the title or the like of the imageis used as additional information is also incorporated in the invention.

[0112]FIG. 11 shows a construction of an image processing apparatuswhich is used in the following embodiment.

[0113] Reference numeral 1000 denotes an image processing unit. Theimage processing unit 1000 sequentially inputs multi-value image data ofM, C, Y, and K from external equipment or another equipment in theapparatus, adds addition information, which will be explainedhereinlater,, to the multi-value image data, and after that, outputs theimage data of each color to a laser light emitting unit 1001. The laserlight emitting unit 1001 emits the laser beam L, which will be explainedhereinlater, modulated in accordance with the inputted image data.

[0114] The photosensitive drum 100 is uniformly charged to apredetermined polarity by the charging device 101. For example, a firstlatent image of magenta is formed on the photosensitive drum 100 by theexposure by the laser beam L. In this case, a desired development biasvoltage is applied to only the developing device Dm of magenta, thelatent image of magenta is developed, and the first toner image ofmagenta is formed on the photosensitive drum 100.

[0115] On the other hand, the transfer paper P is fed at a predeterminedtiming. Just before the front edge of the transfer paper reaches thetransfer start position, a transfer bias voltage (+1.8 kV) of a polarity(for example, plus polarity) opposite to that of the toner is applied tothe transfer drum 102. The first toner image on the photosensitive drum100 is transferred onto the transfer paper P. The transfer paper P iselectrostatically adsorbed onto the surface of the transfer drum 102.After that, the residual magenta toner on the photosensitive drum 100 isremoved by the cleaner 103, thereby preparing for the latent imageformation and the developing step of the next color.

[0116] Subsequently, in a manner similar to the case of magentamentioned above, the second latent image of cyan is formed onto thephotosensitive drum 100 by the laser beam L. The second latent image onthe photosensitive drum 100 is developed by the developing device Dc ofcyan. The second toner image of cyan is formed. The second toner imageof cyan is transferred onto the transfer paper P while matching to theposition of the first toner image of magenta which has already beentransferred to the transfer paper P. In the transfer of the toner imageof the second color, just before the transfer paper reaches the transferunit, a bias voltage of +2.1 kV is applied to the transfer drum 102.

[0117] Similarly, the third and fourth latent images of yellow and blackare sequentially formed on the photosensitive drum 100 and aresequentially developed by the developing devices Dy and Db,respectively. The third and fourth toner images of yellow and black aresequentially transferred while matching to the position of the tonerimage which has already been transferred to the transfer paper P. Thus,a full color image in which the toner images of four colors wereoverlapped is formed on the transfer paper P.

[0118] Additional information for fake tracking which is added by theimage processing apparatus of the embodiment will now be described.

[0119]FIG. 12 shows a state where the additional information was addedto the image shown by the inputted image data in the embodiment. In theembodiment as mentioned above, since the additional information is addedto only the plane of Y, FIG. 12 shows the image shown by the plane of Yof the color image comprising planes of Y, M, C, and K.

[0120] Each of dots 1201 existing in FIG. 12 is a dot of a micro areaconstructed by a plurality of pixels. This dot is referred to as anAddOn dot hereinbelow.

[0121] In the diagram, a meshed area 1202 is a unit area showingadditional information which is added to the color image (plane ofyellow) in the embodiment. The unit area 1202 periodically exists in theoriginal color image (plane of yellow). By using this method, withrespect to the color image finally formed after the additionalinformation was added, the additional information can be analyzed withreference to any one of the areas.

[0122] A plurality of lines 1203 called AddOn lines exist in the unitarea 1202. In the embodiment, it is assumed that 16 lines exist in themain scan direction. It is also assumed that as for the foregoing Addondots, one AddOn dot is arranged on each AddOn line in the unit area1202. As will be explained hereinlater, the additional information canshow various information by the position (phase) of the AddOn dot oneach AddOn line. As various information, the product name, manufacturingnumber, manufacturer name, and the like of the image processingapparatus can be allocated.

[0123] A reference dot 1204 to prevent that the arranging direction ofthe AddOn dot to show the additional information. is erroneouslydiscriminated is added in the unit area 1202. The position of thereference dot is always fixed. In the embodiment, the reference dot 1204is added onto the 0th and 7th AddOn lines together with the AddOn dot.By using this method, the AddOn line indicative of the start of the unitarea can be specified and the arranging direction of the AddOn lines 0to 15 can be specified.

[0124]FIG. 14 is a block diagram of an AddOn dot adding processing unitincluded in the image processing unit 1000 in FIG. 11. The additionalinformation (product name of the apparatus, manufacturing number,manufacturer name, and the like) stored in an EEPROM 1401 isautomatically loaded into a register 1402 in the CPU when the powersource of the image processing apparatus is turned on.

[0125]FIG. 13 shows an internal construction of the register 1402. Inthe register 1402, codes are stored in addresses F000 to F00A. Total 12bits comprising 8 bits of the address F000 shown by a hatched region andupper 4 bits of the address F0001 shown by a hatched region in thediagram correspond to an area only for use of the manufacturer name(manufacturer ID) mentioned above. The peculiar ID number assigned everymanufacturer who manufactured the image processing apparatus is storedin this area. The codes indicative of the product name of the imageprocessing apparatus, manufacturing number, and the like which haveuniquely been determined by each manufacturer are stored in the otherareas (lower 4 bits of the address F0001, and F002 to F00A).

[0126] Besides the foregoing additional information, the fixed bit inwhich a fixed value is stored and the parity bits for parity check arealso stored in the register 1402.

[0127] When the image processing apparatus receives a command to printthe color image, the foregoing additional information (product name ofthe apparatus, manufacturing number, manufacturer name, and the like) isinputted to an encipherment circuit 1405 and is enciphered.

[0128] The enciphered additional information is inputted to a paritycheck circuit 1406 and the parity and the fixed bit are checked. When anerror occurs here, it is regarded that the additional information hasbeen remodeled, thereby performing a control to stop the printingoperation.

[0129] A main scan counter 1407 executes the counting operation inresponse to the clock signal PCLK in the main scan direction of theimage data and generates an ON signal at a position where the AddOn dotshould be added in accordance with a code which is loaded by the paritycheck 1406. A subscan counter 1408 executes the counting operation inaccordance with the clock signal BD in the subscan direction andgenerates an ON signal in the AddOn line.

[0130] An AddOn dot generation circuit 1409 receives the AddOndot-shaped parameter which is stored into an ROM 1403 in the CPU, formsthe AddOn dot only when all of an AddOn permission signal which isturned on only when the yellow plane of the image data is transmitted,the main scan counter 1407, and the subscan counter 1408 are ON, turnson the AddOn signal, and sends.

[0131] When the AddOn signal is OFF, an AddOn adding circuit 1404transmits as it is to the image data which is inputted. When the AddOnsignal is ON, the AddOn adding circuit 1404 converts it into the AddOndot and sends it. Thus, the additional information (AddOn dot) is formedas shown in FIG. 12.

[0132] A method of analyzing the additional information added to theimage data in the embodiment, namely, a method of showing the additionalinformation by the AddOn dot will now be described.

[0133]FIG. 15 enlargedly shows the n-th and (n+1)th AddOn lines in theunit area 1202 in FIG. 12. Explanation will now be made with respect tothe (n+1)th AddOn line. A phase difference using the AddOn dot on then−th AddOn line as a reference is assigned to 0 to 7 (3 bits) as shownin the diagram, thereby allowing the AddOn dot to be added to theposition corresponding to the 3-bit information to be added in the(n+1)th AddOn line. Therefore, information of 3 bits can be expressed byone AddOn line (AddOn dot). Thus, since there are 16 AddOn lines in theembodiment, additional information of total 48 bits can be added.

[0134] However, the invention is not limited to this method but theadditional information can be also added by another method. For example,by adding a plurality of AddOn dots onto each AddOn line, moreadditional information can be also added.

[0135] As for the analysis of the phase difference, for example, thecolor image to which the additional information was added is read by ascanner, only the image of the plane of Y (yellow) is extracted andtransmitted to a host computer, and an interval between the AddOn dotsis measured on a monitor of the host computer, so that the phasedifference can be measured. On the basis of the measured phasedifference, the code of each AddOn line is searched and the searchedcodes are arranged as shown in FIG. 16 and are binarized. After that,the binary codes are assigned as address information of a00 to a30 andb00 to b112. a00 to a32 indicate the manufacturer ID (manufacturer name)and a22, a30, a31, and a32 are parity bits.

[0136] First, when the manufacturer ID is analyzed, a00 to a32 arearranged as shown in FIG. 17 and it is confirmed that a22, a30, a31, anda32 become even parities in the arrow direction in the diagram. If anerror is detected by the parity check, it is regarded that there is areading mistake (analysis mistake) of the manufacturer ID and theoperation is re-executed from the measurement.

[0137] If no error is detected by the parity check, a00 to a21 arearranged as follows, thereby obtaining the manufacturer ID.

[0138] Manufacturer,ID=(a21, a20, a12, a11, a10, a02, a01, a00)

[0139] In the example of FIG. 16, the manufacturer ID is as follows.

[0140] Manufacturer ID =(a21, a20, a12, a11, a10, a02, a01, a00)

[0141] =0, 0, 1, 0, 0, 0, 1, 0(B)

[0142] =34(D)

[0143] The manufacturer who manufactured the image processing apparatuswhich was used for the formation of the color image is analyzed by theobtained manufacturer ID.

[0144] After the manufacturer ID was analyzed, the additionalinformation such as product name, manufacturing number, and the like canbe analyzed by the method according to each manufacturer. This isbecause there is a possibility such that the adding method of theadditional information such as product name, manufacturing number, andthe like differs every manufacturer. Therefore, the parity bits areindependently added to the manufacturer ID and the product name andmanufacturing number, respectively.

[0145] Subsequently, with respect to b00 to b112 (including the paritybits) showing the additional information such as product name,manufacturing number, and the like, they are analyzed (parity check)independently of the manufacturer ID.

[0146] As for the additional information of b00 to b112, after thedecoding of the additional information of b00 to b112 and the paritycheck were performed by using the method suitable for each manufacturer,the model number, apparatus number, and the like are obtained.

[0147] As mentioned above, by independently adding the parity bits tothe manufacturer ID (manufacturer name) and the product name andmanufacturing number (model number, apparatus number, and the like canbe also used), even in case of adding the additional information of themanufacturer ID and the additional information such as product name,manufacturing number, and the like to the image by different methods,whether the various analyzed additional information is accurate or notcan be certainly discriminated.

[0148]FIG. 19 shows a conceptual diagram of the additional informationsuch as manufacturer ID, product name, and manufacturing number added inthe above embodiment.

[0149] In FIG. 19, reference numeral 1202 corresponds to the unit area1202 in FIG. 12. The manufacturer ID is added (expressed) by using theAddOn lines (AddOn lines 0 to 3) of an upper area 1901 of the unit area1202. The product name and the manufacturing number are added(expressed) by using the AddOn lines (AddOn lines 4 to 15) in a lowerarea 1902 of the unit area 1202.

[0150] A procedure to decode the additional information will now beexplained with reference to FIG. 18.

[0151] When the decoding is started, the color image is first read by ascanner. Since the additional information of the embodiment has beenadded to the yellow plane, only the yellow plane is read (step S1).Subsequently, the reference dot is detected, the head of the AddOn lineand the direction of the AddOn line are recognized, and phasedifferences among the AddOn lines 0 to 3 (AddOn lines 15 and 0; 0 and 1;1 and 2; and 2 and 3) are measured (step S2).

[0152] The codes of the Addon lines 0 to 3 are obtained on the basis ofthe measured phase differences (step S3) and are binarized and areassigned to a00 to a32 (step S4). The parity check of FIG. 17 mentionedabove is subsequently executed (step S5). If there is an error, theoperation is re-executed from the measurement of the phase differences(step S2). If there is no error, the manufacturer ID is obtained (stepS6).

[0153] Phase differences among the AddOn lines 4 to 15 are subsequentlymeasured (step S7). On the basis of the measured phase differences, thecodes of the AddOn lines 4 to 15 are obtained (step S8) and arebinarized and are assigned to b00 to b112 (step S9).

[0154] A check is made to see if the manufacturer ID obtained in step S6indicates company A (step S10). If it is the company A, a module forcompany A is activated (step S11). The module for company A rearrangesb00 to b112 in accordance with the rules of company A and the paritycheck and the like are executed. After that, the product name,manufacturing number, and the like are obtained.

[0155] When the manufacturer ID does not indicate company Ain step S10,a check is made to see if it indicates company B (step S12). If itindicates company B, a module for company B is activated (step S13). Ina manner similar to step S11, the module for company B rearranges b00 tob112 in accordance with the rules of company B and the parity check andthe like are executed. After that, the product name, manufacturingnumber, and the like are obtained.

[0156] Similarly, when the manufacturer ID does not indicate company Bin step S12, the manufacturer IDs are sequentially checked only a numberof times as many as the number of registered manufacturers such thatcompany C, company D , . . .

[0157] In the embodiment, although the number of AddOn lines to storethe information of each manufacturer has been fixed to 12 AddOn lines 4to 15, the number of AddOn lines can be also varied every manufacturer.

[0158] In the embodiment, as for the parity bits, parity bits such thatan error detection can be merely performed are added to the manufacturerID corresponding to the area 1901 in FIG. 19 and the product name andmanufacturing number corresponding to the area 1902 in FIG. 19,respectively. However, the invention is not limited to this method. Anerror correction code such that an error of the additional informationcan be corrected can be also provided for each of the additionalinformation corresponding to the areas 1901 and 1902.

[0159] Thus, even if there is an error in the analysis of the additionalinformation, the operation to again read the phase differences can beomitted.

[0160] Further, in the case where it is considered that significance ofthe additional information (manufacturer ID) in the area 1901 is higherthan that of the additional information (product name, manufacturingnumber, and the like) corresponding to the area 1902 such as a casewhere there is a possibility such that unless the additional informationof the area 1901 can be analyzed, the area 1902 cannot be analyzed orthe like, it is also possible to give an error correction code of a higherror correcting ability to the additional information of the area 1901and to give an error correction code of a lower error correcting abilitythan that in the area 1901 to the area 1902.

[0161] By using this method, the important portion of the additionalinformation can be certainly analyzed. Specifically speaking, since themanufacturer ID can be certainly analyzed, a method for subsequentlyanalyzing the product name, manufacturing number, and the like can bedetermined.

[0162] Although the embodiment has been described above on theassumption that the method of adding the manufacturer ID into the area1901 and the method of adding the product name, manufacturing number,and the like into the area 1902 are the same method, the invention isnot limited to this construction but also includes a case where theadding methods of the additional information to the areas 1901 and 1902are different.

[0163] That is, in the embodiment, since the manufacturer ID which canspecify the adding method of the area 1902 is added to the area 1901different from the area 1902, there is an effect such that even if theadding methods of the additional information of the areas 1901 and 1902are different, by sequentially analyzing in accordance with the order ofthe areas 1901 and 1902 as mentioned above, all of the additionalinformation can be sufficiently decoded.

[0164] In the above embodiment, although the additional information hasbeen added by the AddOn dot in which the original image is merelymodulated to the highest density, the invention is not limited to such aconstruction. For example, even if one AddOn dot is constructed bycombining an area to add +α to the density of the original image and anarea to subtract a from the density of the original image, theadditional information can be sufficiently analyzed. In this case, sincethe density of the original image is preserved, the picture quality thatis further higher than that in the foregoing embodiment can bepreferably held. One AddOn dot can be also constructed by combining anarea to modulate the density of the original image to the highestdensity and an area to modulate it to the lowest density. By using thismethod, the AddOn dot can be easily decoded irrespective of the densityof the original image.

[0165] According to the invention as described above, in the case wherepredetermined additional information is added to the input image by oneof a plurality of methods which are generally considered so that it isdifficult to discriminate by the human eyes, another information whichcan specify the method of adding the predetermined additionalinformation is added so that it is difficult to discriminate by thehuman eyes. Therefore, the additional information can be efficientlydecoded from the image to which the predetermined additional informationwas added.

[0166] The first additional information including the error correctioncode having the first error correcting ability is added to the inputimage so that it is difficult to discriminate by the human eyes and thesecond additional information including the error correction code havingthe second error correcting ability different from the first errorcorrecting ability is added so that it is difficult to discriminate bythe human eyes. Therefore, when the importance of a plurality ofadditional information which is added to the image so that it isdifficult to discriminate by the human eyes is different, the additionalinformation having the high importance can be certainly decoded.

[0167] The invention is not limited to each of the above embodiments butcan be applied as a part of a system constructed by a plurality ofequipment (for example, host computer, interface equipment, reader,printer, and the like) or can be also applied to a part of an apparatuscomprising one equipment (for instance, copying apparatus or facsimileapparatus).

[0168] The invention is not limited to only the apparatus and method forrealizing the above embodiments. The invention also incorporates a casewhere program codes of software to realize the embodiment are suppliedto a computer (CPU, MPU) in the system or apparatus and the computer ofthe system or apparatus makes the various devices operative inaccordance with the program codes, thereby realizing the embodiment.

[0169] In this case, the program codes themselves of the softwarerealize the function of the embodiment. The program codes themselves andmeans for supplying the program codes to the computer, specificallyspeaking, a storage medium in which the program codes have been storedare also incorporated in the scope of the invention.

[0170] As a storage medium to store the program codes as mentionedabove, for example, it is possible to use a floppy disk, a hard disk, anoptical disk, a magnetooptic disk, a CD-ROM, a magnetic tape, anon-volatile memory card, an ROM, or the like.

[0171] Not only in the case where the computer controls various devicesin accordance with only the supplied program codes, thereby realizingthe function of the embodiment but also in the case where the programcodes cooperate together with the OS (Operating System) which operateson the computer or another application software or the like, the aboveprogram codes are also incorporated in the scope of the invention.

[0172] Further, the invention also incorporates a case where thesupplied program codes are stored into a memory provided for a functionexpansion board of the computer or a function expanding unit connectedto the computer and, after that, a CPU or the like provided for thefunction expansion board or function expanding unit executes a part orall of the actual processes on the basis of an instruction of theprogram codes and the embodiment is realized by the processes.

[0173] The present invention is not limited to the foregoing embodimentsbut many modifications and variations are possible within the spirit andscope of the appended claims of the invention.

What is claimed is:
 1. An image processing apparatus comprising: addingmeans for periodically adding first additional information to an inputimage by a first period so that it is difficult to discriminate by thehuman eyes and for periodically adding second additional informationdifferent from said first additional information by a second perioddifferent from said first period so that it is difficult to discriminateby the human eyes; and output means for outputting the image to whichpredetermined additional information was added by said adding means toan image forming unit.
 2. An apparatus according to claim 1, whereinsaid first period is shorter than said second period.
 3. An apparatusaccording to claim 1, wherein said first additional information isinformation to specify said image processing apparatus.
 4. An apparatusaccording to claim 1, wherein said second additional information isinformation to specify said image processing apparatus.
 5. An apparatusaccording to claim 3, wherein said first additional information is an IDof a manufacturer who manufactured said image processing apparatus. 6.An apparatus according to claim 4, wherein said second additionalinformation is an apparatus number or a model number of said imageprocessing apparatus.
 7. An apparatus according to claim 1, furtherhaving said image forming unit.
 8. An apparatus according to claim 1,wherein said input image is a color image constructed by a plurality ofcolors and said adding means adds said first or second additionalinformation to a partial color instead of all of said plurality ofcolors.
 9. An apparatus according to claim 1, wherein said adding meansadds said first or second additional information as a plurality of dots.10. An apparatus according to claim 9, wherein said first or secondadditional information is expressed by phase differences among saidplurality of dots.
 11. An apparatus according to claim 9, wherein eachof said dots is constructed by combining an area to modulate an image tothe highest density and an area to modulate the image to the lowestdensity.
 12. An apparatus according to claim 9, wherein each of saiddots is constructed by combining an area to modulate an image by only +αand an area to modulate the image by only −α.
 13. An image processingmethod comprising: an adding step of periodically adding firstadditional information to an input image by a first period so that it isdifficult to discriminate by the human eyes and periodically addingsecond additional information different from said first additionalinformation by a second period different from said first period so thatit is difficult to discriminate by the human eyes; and an outputtingstep of outputting the image to which predetermined additionalinformation was added by said adding step to an image forming unit. 14.A storage medium for storing an image processing program in a statewhere said program can be read out from a computer, said programcomprising: an adding step of periodically adding first additionalinformation to an input image by a first period so that it is difficultto discriminate by the human eyes and periodically adding secondadditional information different from said first additional informationby a second period different from said first period so that it isdifficult to discriminate by the human eyes; and an outputting step ofoutputting the image to which predetermined additional information wasadded by said adding step to an image forming unit.
 15. An imageprocessing apparatus comprising: adding means for adding informationconsisting of first additional information and second additionalinformation to an input image every unit area which is periodicallyassigned; switching means for switching a positional relation between anarea showing said first additional information and an area showing saidsecond additional information in said unit area; and output means foroutputting the image to which predetermined additional information wasadded by said adding means to an image forming unit.
 16. An apparatusaccording to claim 15, wherein said first additional information isinformation to specify said image processing apparatus.
 17. An apparatusaccording to claim 15, wherein said second additional information isinformation to specify said image processing apparatus.
 18. An apparatusaccording to claim 16, wherein said first additional information is anID of a manufacturer who manufactured said image processing apparatus.19. An apparatus according to claim 17, wherein said second additionalinformation is an apparatus number or a model number of said imageprocessing apparatus.
 20. An apparatus according to claim 15, furtherhaving said image forming unit.
 21. An apparatus according to claim 15,wherein said input image is a color image constructed by a plurality ofcolors and said adding means adds said first or second additionalinformation to a partial color instead of all of said plurality ofcolors.
 22. An apparatus according to claim 15, wherein said addingmeans adds said first or second additional information as a plurality ofdots.
 23. An apparatus according to claim 22, wherein said first orsecond additional information is expressed by phase differences amongsaid plurality of dots.
 24. An apparatus according to claim 22, whereineach of said dots is constructed by combining an area to modulate animage to the highest density and an area to modulate the image to thelowest density.
 25. An apparatus according to claim 22, wherein each ofsaid dots is constructed by combining an area to modulate an image byonly +α and an area to modulate the image by only −α.
 26. An imageprocessing method comprising: an adding step of adding informationconsisting of first additional information and second additionalinformation to an input image every unit area which is periodicallyassigned; a switching step of switching a positional relation between anarea showing said first additional information and an area showing saidsecond additional information in said unit area; and an outputting stepof outputting the image to which predetermined additional informationwas added by said adding step to an image forming unit.
 27. A storagemedium for storing an image processing program in a state where saidprogram can be read out from a computer, said program comprising: anadding step of adding information consisting of first additionalinformation and second additional information to an input image everyunit area which is periodically assigned; a switching step of switchinga positional relation between an area showing said first additionalinformation and an area showing said second additional information insaid unit area; and an outputting step of outputting the image to whichpredetermined additional information was added by said adding step to animage forming unit.
 28. An image processing apparatus comprising: addingmeans for adding first additional information to an input image by afirst method so that it is difficult to discriminate by the human eyesand for adding second additional information by a second method so thatit is difficult to discriminate by the human eyes; and output means foroutputting the image to which predetermined additional information wasadded by said adding means to an image forming unit, wherein said firstadditional information is information which can specify said secondmethod.
 29. An apparatus according to claim 28, wherein said firstadding method and said second adding method are different.
 30. Anapparatus according to claim 28, wherein said first adding method andsaid second adding method are the same.
 31. An apparatus according toclaim 28, wherein said input image is a color image constructed byplanes of a plurality of colors, and said adding means adds said firstand second additional information to only a partial plane among saidplanes of said plurality of colors.
 32. An apparatus according to claim28, wherein said first additional information is a manufacturer ID ofsaid image processing apparatus.
 33. An apparatus according to claim 28,wherein said second additional information is a model number or aproduct name of said image processing apparatus.
 34. An apparatusaccording to claim 28, wherein said second additional information is anapparatus number or a manufacturing number of said image processingapparatus.
 35. An apparatus according to claim 28, further comprisingsaid image forming unit.
 36. An apparatus according to claim 28, whereinsaid first additional information is a pattern constructed by aplurality of dots.
 37. An apparatus according to claim 28, wherein saidsecond additional information is a pattern constructed by a plurality ofdots.
 38. An apparatus according to claim 28, wherein said additionalinformation is periodically added to said input image.
 39. An apparatusaccording to claim 28, wherein said first additional information isadded to a first area of said input image and said second additionalinformation is added to a second area different from said first area.40. An image processing method comprising: an adding step of addingfirst additional information to an input image by a first method so thatit is difficult to discriminate by the human eyes and adding secondadditional information by a second method so that it is difficult todiscriminate by the human eyes; and an outputting step of outputting theimage to which predetermined additional information was added by saidadding step to an image forming unit, wherein said first additionalinformation is information which can specify said second method.
 41. Astorage medium for storing an image processing program in a state wheresaid program can be read out from a computer, said program comprising:an adding step of adding first additional information to an input imageby a first method so that it is difficult to discriminate by the humaneyes and adding second additional information by a second method so thatit is difficult to discriminate by the human eyes; and an outputtingstep of outputting the image to which predetermined additionalinformation was added by said adding step to an image forming unit; andin which said first additional information is information which canspecify said second method.
 42. An image processing apparatuscomprising: adding means for adding first additional informationincluding an error correction code having a first error correctingability to an input image so that it is difficult to discriminate by thehuman eyes and for adding second additional information including anerror correction code having a second error correcting ability differentfrom said first error correcting ability so that it is difficult todiscriminate by the human eyes; and output means for outputting theimage to which predetermined additional information was added by saidadding means to an image forming unit.
 43. An apparatus according toclaim 42, wherein said first additional information is information whichcan specify an adding method of said second additional information bysaid adding means.
 44. An apparatus according to claim 42, wherein saidfirst error correcting ability is higher than said second errorcorrecting ability.
 45. An apparatus according to claim 42, wherein amethod of adding said first additional information and a method ofadding said second additional information are different.
 46. Anapparatus according to claim 42, wherein a method of adding said firstadditional information and a method of adding said second additionalinformation are the same.
 47. An apparatus according to claim 42,wherein said input image is a color image constructed by planes of aplurality of colors, and said adding means adds said first and secondadditional information to only a partial plane among said planes of saidplurality of colors.
 48. An apparatus according to claim 42, whereinsaid first additional information is a manufacturer ID of said imageprocessing apparatus.
 49. An apparatus according to claim 42, whereinsaid second additional information is a model number or a product nameof said image processing apparatus.
 50. An apparatus according to claim42, wherein said second additional information is an apparatus number ora manufacturing number of said image processing apparatus.
 51. Anapparatus according to claim 42, further comprising said image formingunit.
 52. An apparatus according to claim 42, wherein said firstadditional information is a pattern constructed by a plurality of dots.53. An apparatus according to claim 42, wherein said second additionalinformation is a pattern constructed by a plurality of dots.
 54. Anapparatus according to claim 42, wherein said additional information isperiodically added to said input image.
 55. An apparatus according toclaim 42, wherein said first additional information is added to a firstarea of said input image and said second additional information is addedto a second area different from said first area.
 56. An image processingmethod comprising: an adding step of adding first additional informationincluding an error correction code having a first error correctingability to an input image so that it is difficult to discriminate by thehuman eyes and adding second additional information including an errorcorrection code having a second error correcting ability different fromsaid first error correcting ability so that it is difficult todiscriminate by the human eyes; and an outputting step of outputting theimage to which predetermined additional information was added by saidadding step to an image forming unit.
 57. A storage medium for storingan image processing program in a state where said program can be readout from a computer, said program comprising: an adding step of addingfirst additional information including an error correction code having afirst error correcting ability to an input image so that it is difficultto discriminate by the human eyes and adding second additionalinformation including an error correction code having a second errorcorrecting ability different from said first error correcting ability sothat it is difficult to discriminate by the human eyes; and anoutputting step of outputting the image to which predeterminedadditional information was added by said adding step to an image formingunit.